Well, Grune aside, you have, I think, got all the right answers, but a lot of wrong answers as well!
The question was ONE-TIME villains from series one, who became recurring villains in SERIES TWO (or two to four, depending on how you count it). I shall deal with the wrong answers first. Therefore:
Safari Joe and Spidera don’t count, they were technically one-time villains from season 1 who were brought back once at the end of season 1 in “Fond Memories”.
The Technopede is also technically a one-time season 1 villain that reappeared once later in “Mechanical Plague”, along with the Mutant Warbot.
The Driller and was a recurring season 1 villain who didn’t appear at all in season 2, likewise Mole Master.
I’m not entirely sure Captain Shiner counts, as his only second season appearance was in Thundercats Ho! - split into five episodes, but a single movie.
And onto the correct answers:
The robot pirate - “Captain Cracker” appeared once in season 1, then in two different later series episodes.
The Berserkers appeared once in season 1, and then several times in season 2. (Even Hammerhand technically appeared only once in season 1, although his ghost reappeared in “Spitting Image”)
Grune - once in season 1, then he appeared in “Thundercats HO!” and “Return To Thundera”.
Anyhow, Tygra Rules, you got more correct answers technically, so it’s your turn.